1. Field of the Invention
This invention relates to cutter inserts of a generally quadrilateral shape having a peripheral cutting edge and an end cutting edge, such cutter inserts being adapted to be employed in a cutter such as a face milling cutter, a boring cutter and a side milling cutter.
2. Prior Art
FIG. 1 shows a face milling cutter 10 employing conventional cutter inserts 11 of a rectangular shape. The face milling cutter 10 comprises a body 12 including a base portion 13 of a circular cross-section having a forward end face 14, a rearward end face 15 and a circumferential surface 16 lying between the forward end face 14 and the rearward end face 15. A boss 17 extends coaxially from the base portion 13 at its rearward face 15 and is adapted to be fixedly secured to a spindle of a milling machine.
The base portion 13 of the cutter body 12 has a plurality of generally radially outwardly-opening recesses 20 formed in the circumferential surface 16 in circumferentially spaced relation to each other and disposed adjacent to the forward end face 14. Each of the recesses 20 has a generally channel-shaped cross-section and has a first flat bearing surface 21 sloping radially outwardly in a direction away from the forward end face 14 and extending to the circumferential surface 16. The recess 20 also has a forward end wall 22 which faces in a direction away from the forward end face 14 and is sloping radially outwardly toward the forward end face 14. The forward end wall 22 is defined by a forward end projection 23. The forward end wall 22 is stepped or raised at its distal end to form a second flat bearing surface 24 which is disposed at right angles to the first bearing surface 21.
The rectangular insert 11 of the indexable type comprises a plate of metal such as high speed steel. The rectangular insert 11 is defined by a front face 25, a rear face parallel to the front face 25, a pair of parallel longer side faces 26 and a pair of parallel shorter side faces 27. Four corners of the rectangular insert 11 are chamfered to form four corner faces. Two diagonal corner faces are sloping from the front face 25 to the rear face and directed to each other. Two corner edges 30 defined by respective corner faces and the front face 25 serve as auxiliary cutting edges which constitute end cutting edges. Two edges 26a defined by the two longer side faces 26 and the front face 25 serve as two main cutting edges, respectively, which constitute peripheral cutting edges. Similarly, the other two diagonal corner faces are sloping from the rear face to the front face 25 and directed toward each other. Two corner edges 30 defined by respective corner faces and the rear face serve as auxiliary cutting edges. Two edges 26a defined by the two longer side faces 26 and the rear face serve as two main cutting edges, respectively.
The rectangular insert 11 is received in the recess 20 with one longer side face 26 held against the first bearing surface 21 and with one shorter side face 27 held against the second bearing surface 24. In this condition, the main or peripheral cutting edge 26a remote from the first bearing surface 21 and its mating auxiliary or end cutting edge 30 are disposed in their respective indexed positions, as shown in FIG. 1.
The auxiliary or end cutting edges 30 of the inserts 11 serve to provide a finish surface of a workpiece processed by the face milling cutter 10. The cutter body 12 and each insert 11 are so designed that the indexed auxiliary cutting edges 30 of all the inserts are disposed substantially in a common plane perpendicular to an axis X of rotation of the cutter body 12. Actually, however, there are occasions when the indexed auxiliary cutting edges 30 are disposed slightly out of their indexed position, i.e., the above-mentioned common plane. This will result in an unsatisfactory finish surface of the workpiece.